Concrete slabs are commonly used, either as floors or walls, in the construction of modern structures. One common technique for floors is to use blocks, typically formed from polystyrene, to form part of the formwork for the slab. The use of such blocks has several advantages, including filling space that would otherwise be filled with concrete (saving material costs) or requiring some form of interior enclosure as part of the formwork (saving labor costs in construction and removal of the interior formwork), and is a relatively quick and efficient method of forming a formwork for the slab. Concrete slabs formed in this way are commonly referred to as ribbed or waffle slabs.
One problem with this technique is that the blocks must be placed precisely in relation to one another, including the spacing between blocks, to ensure the poured ribs of the foundation slab (i.e., the space between the blocks when filled with concrete) are of the correct size. Although spacers can be used to assist with this, the process of using the spacers for each block can be time consuming, and problems can arise if any one block in the array of blocks is accidentally moved.
Another problem with this technique is that the blocks must be fixed in place so that they don't move around when the concrete for the slab is poured. This is typically done by inserting reinforcing bars (“rebars”) into the spaces between the blocks and tying the rebars together to form a rigid network around the blocks. When this inter-block network is tied to the rebars placed above the blocks, the whole structure of rebars and blocks is held in place.
Forming the inter-block reinforcing network is labor and time intensive, and can be one of the main limiting factors in reducing the time required to get the formwork ready for pouring the slab. As time is often critical when constructing a building, any reduction in the time required to form the slab can translate into savings in the overall cost of the structure. Furthermore, the additional labor required to tie the rebars together can add significantly to the cost of forming the slab. Accordingly, an improved method and apparatus for forming concrete slabs may be beneficial. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.